Can your mood come from your gut? Cautious response: the microbiota could communicate with the brain, but it is not enough to explain or treat depression. In the show “The advice of Doctor Kierzek” on ICI, Dr Gérald Kierzek, emergency doctor and medical director of True Medical details these ideas and everyday actions.
Microbiota and morality: a plausible dialogue, not proof of causality
The intestinal microbiota corresponds to the billions to tens of thousands of billions of microorganisms that live in the intestine: bacteria, viruses, yeasts and other microbes. Long reduced to digestion, it is today studied for its exchanges with the brain, via what we call the gut-brain axis.
The doctor cites several possible pathways: neurons in the digestive tract which transmit information, the vagus nerve, which he compares to a telephone cable between the stomach and the brain, and molecules produced by intestinal bacteria which pass into the blood. He also mentions inflammatory pathways, but with caution: in humans, these mechanisms remain avenues for research to understand the influence of the microbiota on mental health.
The most important nuance comes from the chronicle itself. Dr Kierzek insists that scientific observations should not be transformed into therapeutic certainty:
“In studies, we talk about association, not cause and effect. It’s not direct causality”
Work carried out in mice, notably by Inserm, the Pasteur Institute and the CNRS, suggests that the vagus nerve participates in the link between microbiota and depressive-type behaviors after microbiota transfer. But a result in mice does not prove that a food or supplement directly improves morale in humans. Association and causality must therefore remain separate.
Gestures to prioritize without treating morale
On a practical level, Dr Kierzek gives a simple direction: diversity. The idea is not to aim for a perfect plate, but to gradually increase the sources of fiber and plants, according to your tastes, your budget, your health constraints and your digestive tolerance.
The avenues cited in the column are concrete:
- Gradually increase fiber with vegetables, fruits, legumes such as lentils or chickpeas, whole grains and oilseeds;
- Keep the benchmark of around 30 g of fiber per day as an order of magnitude, within the official adult range of 25 to 40 g per day;
- Vary the plants, with the idea of 30 different plants per week, aromatic herbs and spices included, as a challenge for diversification and not as an official rule;
- Try fermented foods if you tolerate them: yogurt, kefir, sauerkraut or certain cheeses, with no guaranteed benefit on morale.
For fibers, better to move forward step by stepespecially in cases of irritable bowel syndrome, digestive disease or bloating. This progression makes the change more comfortable and more lasting.
Vigilance is also required on raw milk cheese, cited in the show: it is not suitable for all populationsparticularly pregnant women, young children, elderly or immunocompromised people. Fermented foods can be part of a varied diet, but they are not essential for taking care of your microbiota on a daily basis.
The doctor also advises limiting ultra-processed products, excess sugar and alcohol. To be made without feeling guilty: these choices often depend on the time available, the budget, the food environment or medical constraints. The realistic goal is to make more room, where possible, for minimally processed foods rich in fiber.
Dr Kierzek finally reminds that the microbiota does not only depend on the plate: physical activity, regular sleep and reasonable use of antibiotics also count in a healthy lifestyle. On this last point, you should never take an antibiotic without a prescription, nor interrupt a prescribed treatment without medical advice. The issue is to avoid unnecessary doses, not to refuse a necessary medication.
In case of persistent sadness, significant anxiety, depressive symptoms, suicidal thoughts, eating disorder or chronic illness, this advice does not replace medical or psychological care. In a situation of immediate danger, you must contact the emergency services.